Acetobacterium dehalogenans is able to utilize the methyl
group of phenyl methyl ethers as energy source. The methyl moiety is
converted to acetate via the carbon monoxide dehydrogenase pathway. The
anoxic ether cleavage reaction catalyzed by O-demethylase is studied. The enzyme consists of four separate proteins. One of the proteins contains vitamin B12
as prosthetic group. The methyl group of the phenyl methyl ethers is
transferred by a methyl transferase I to the cobalt of the corrinoid
protein and then by a second methyl transferase II to tetrahydrofolate.
The fourth component ("activating enzyme" AE) has a "repair" function
in the reductive, ATP-dependent reactivation of the cobalamin. This
reaction and the interaction between the four components are currently
investigated in our laboratory. All four components could be identified
and their role in O-demethylation could be elucidated. The
genes have been cloned, sequenced and characterized, and studies on the
evolution of the methyl transferase I as well as on the activation
mechanism exerted by AE are currently underway in our laboratory.

Several anaerobic bacteria are able to reductively dechlorinate chlorinated hydrocarbons and to gain energy from this process (dehalorespiration). Two of these bacteria, designated Sulfurospirillum multivorans (formerly: Dehalospirillum multivorans) and Desulfitobacterium sp. strain PCE-S, mediate the reductive dechlorination of tetrachloroethene (PCE) in their energy metabolism. The PCE dehalogenase has been purified from both organisms. It is a vitamin B12 containing protein, which additionally carries two 4Fe-4S clusters. The corrinoid of S. multivorans is a unique, novel type, norpseudo-B12 The PCE dehalogenase represents a new type of enzymes involving a redox-active cobalamin as prosthetic group. The gene encoding for PCE dehalogenase of S. multivorans was cloned in E. coli and sequenced. At present we are studying the enzymatic reaction mechanism and the structure of the enzyme as well as the regulation of the localization and the expression of the enzyme. In addition, the mechanism of energy conservation via dehalorespiration is investigated.

For more information, please visit also the website of our Research Unit (Forschergruppe FOR1530) on the "Anaerobic Biological Dehalogenation".